The invention relates to reducing sand production from well formations.
To produce hydrocarbons from a subterranean formation, a wellbore is drilled through the formation. The wellbore may be vertical, deviated, or horizontal. After the wellbore is drilled, it can be lined with a casing or liner that may be cemented to the formation. Next, a perforating gun string can be lowered to the desired depth (or desired depths), with the perforating gun string shot to create desired perforations in the surrounding casing or liner and cement sheath and to extend perforations into the surrounding formation.
Following perforation, fracturing may be performed for various purposes. One type of fracturing is hydraulic fracturing, which includes injecting fluids down the wellbore and into the formation through the perforations in the casing and formation. The fluid is injected at a sufficiently high pressure to induce the parting of the formation. Generally, the fractures extend along a direction that is perpendicular to the plane of minimum stress in the formation. Proppants are also used in the hydraulic fracturing to prop or hold open the created fractures after the hydraulic pressure used to generate the fracture is relieved. The fracture filled with the proppant creates a narrow but very conductive path through the formation to the wellbore.
Originally, hydraulic fracturing was used to stimulate the well for improved productivity. By creating the fractures, a large part of the production flow comes into the wellbore through the fractures. More recently, field experience has shown that fracturing can also be used for sand control.
In producing reservoir fluids from unconsolidated or weakly consolidated reservoirs, sand and other particulates may be produced along with the reservoir fluids (e.g., oil, gas or water). The production of formation sand and other particulates creates a number of potential problems, including lost or reduced production due to sand accumulating in the wellbore. The sand and other particulates that flow through the wellbore may also cause damage to downhole and surface equipment. Further, any sand or other particulates that are produced to the well surface poses a disposal problem, since disposal of the sand or other particulates is typically costly. Damage to the casing or liner may also occur, since production of sand leaves void spaces behind the casing which can reduce the support for the casing, causing collapse or buckling.
A common technique for controlling sand production is to use gravel pack procedures. A typical gravel pack completion includes a screen that is surrounded by gravel which filters out sand and other particulates as the produced fluids flow from the formation through the screen and into the production tubulars. However, gravel-packing procedures are associated with various shortcomings, including an increase in damage effects.
As noted above, an alternative technique for sand control is hydraulic fracturing. Fracturing reduces the drawdown pressure for a given production rate and can maintain the drawdown pressure below the critical pressure for sand production. In another application, perforating to eliminate out-of-phasing perforations following fracturing can also be used to control formation sand production by physically keeping the formation from the wellbore with the proppant pack.
Although it is known that fracturing can be used for sand control, a convenient method and apparatus has not been provided to accurately predict how effective a fracturing operation may be for sand control purposes.
In general, according to one embodiment, a method of sand control in a wellbore comprises accessing representation information defining a relationship between fluid flow through one or more out-of-phase perforations and a function of fracture conductivity and formation permeability. One or more of a fracture characteristic and a fluid flow rate are selected based on the representation information to achieve sand control.
Other features and embodiments will become apparent from the following description, from the drawings, and from the claims.